Power element and expansion valve using same

ABSTRACT

Provided are a power element and an expansion valve using same that are capable of suppressing local deformation of a diaphragm while ensuring the transfer efficiency of a refrigerant. A power element includes a diaphragm; an upper lid member that is overlapped on one surface in the vicinity of the outer circumference of the diaphragm and forms a pressure working chamber PO with the diaphragm; a receiving member that is overlapped on another surface in the vicinity of the outer circumference of the diaphragm and forms a refrigerant inflow chamber LS with the diaphragm; and a stopper member housed in the refrigerant inflow chamber LS and in contact with the diaphragm, wherein the diaphragm is displaced within a range from a neutral position to a position displaced from the neutral position toward the upper lid member side.

TECHNICAL FIELD

The present invention relates to a power element and an expansion valve using same.

BACKGROUND OF THE INVENTION

Conventionally, in the refrigeration cycles used in air conditioners or the like mounted in automobiles, temperature-sensitive temperature expansion valves are used that adjust the amount of refrigerant passing through according to the temperature. In such temperature expansion valves, power elements are employed to drive the valve element with the pressure of an enclosed working gas.

The power element provided in the expansion valve illustrated in Patent Document 1 is provided with a diaphragm, an upper lid member that forms a pressure working chamber in which a working gas is sealed between the diaphragm, a receiving member provided with a through hole in its central portion and arranged on the opposite side of the upper lid member with respect to the diaphragm, and a stopper member disposed in a fluid inflow chamber formed between the diaphragm and the receiving member and connected to an operation rod for driving a valve element. The diaphragm is made of a thin and flexible metal plate.

If the temperature of the refrigerant flowing into the fluid inflow chamber is low, heat is taken from the working gas in the pressure working chamber to cause contraction, and if the temperature of the refrigerant is high, heat is applied to the working gas in the pressure working chamber to cause expansion. Since the diaphragm deforms according to the contraction/expansion of the working gas, the valve element can be opened and closed via the stopper member and the operating rod in accordance with the amount of deformation, whereby adjustment of the flow rate of the refrigerant passing through the expansion valve can be performed.

CITATION LIST Patent Documents

-   [Patent Document 1] Japanese Unexamined Patent Application     Publication No. 2019-163896

SUMMARY OF INVENTION Technical Problem

Incidentally, in general refrigeration cycles, a strainer is provided in order to capture foreign matter mixed in the refrigerant flowing through the pipe. However, minute foreign matter may pass through the strainer and enter the power element. In such a case, foreign matter may enter between the receiving member and the diaphragm, which may cause local deformation of the diaphragm. On the other hand, if the strainer is provided with the ability to capture even minute foreign matter, the pressure loss in the strainer may increase and the transfer efficiency of the refrigerant in the refrigeration cycle may deteriorate.

Accordingly, an object of the present invention is to provide a power element and an expansion valve using same that are capable of suppressing local deformation of a diaphragm or the like while ensuring the transfer efficiency of a refrigerant.

Means for Solving the Problems

In order to achieve the above object, a power element according to the present invention includes a diaphragm; an upper lid member that comes into contact with an outer circumferential portion of the diaphragm and that forms a pressure working chamber with the diaphragm; a receiving member that comes into contact with an outer circumferential portion of the diaphragm and that forms a refrigerant inflow chamber with the diaphragm; and a stopper member housed in the refrigerant inflow chamber and in contact with the diaphragm, wherein the diaphragm is displaced within a range from a neutral position to a position displaced from the neutral position toward the upper lid member side.

Further, an expansion valve according to the present invention includes a power element; a valve main body provided with a refrigerant flow path communicating with the refrigerant inflow chamber, having a valve chamber and a valve seat; a valve element disposed in the valve chamber; a coil spring that presses the valve element toward the valve seat; and an operation rod having one end in contact with the valve element, wherein: the power element includes a diaphragm, an upper lid member that comes into contact with an outer circumferential portion of the diaphragm and that forms a pressure working chamber with the diaphragm, and a receiving member that comes into contact with an outer circumferential portion of the diaphragm and that forms a refrigerant inflow chamber with the diaphragm, and the diaphragm is displaced within a range from a neutral position to a position displaced from the neutral position toward the upper lid member side by a pressure difference between a pressure working chamber of the power element and the refrigerant inflow chamber, and drives the valve element against a biasing force of the coil spring.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a power element and an expansion valve using same that are capable of suppressing local deformation of a diaphragm or the like while ensuring the transfer efficiency of a refrigerant.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view schematically illustrating an example in which the expansion valve according to the present embodiments is applied to a refrigerant circulation system.

FIG. 2 is an enlarged cross-sectional view of the power element.

FIG. 3 is an enlarged cross-sectional view illustrating a portion A of FIG. 2 .

FIG. 4 is a schematic cross-sectional view illustrating an expansion valve according to the second embodiment.

FIG. 5 is a cross-sectional view of the power element 8A according to the second embodiment.

FIG. 6 is a cross-sectional view illustrating an enlarged portion B of FIG. 4 according to the second embodiment.

DESCRIPTION OF EMBODIMENT(S)

Hereinafter, the embodiments according to the present invention will be described with reference to the figures.

(Definition of Directions)

In the present specification, the direction extending from the valve element 3 toward the operation rod 5 is defined as the “upward direction,” and the direction extending from the operation rod 5 toward the valve element 3 is defined as the “downward direction.” Accordingly, in the present specification, the direction extending from the valve element 3 toward the operation rod 5 is referred to as the “upward direction” regardless of the orientation of the expansion valve 1.

First Embodiment

An overview of an expansion valve 1 including a power element according to the first embodiment will be described with reference to FIG. 1 . FIG. 1 is a schematic cross-sectional view schematically illustrating an example in which the expansion valve 1 according to the present embodiments is applied to a refrigerant circulation system 100. In the present embodiment, the expansion valve 1 is fluidly connected to a compressor 101, a condenser 102, and an evaporator 104. L is set as the axis of the expansion valve 1.

In FIG. 1 , the expansion valve 1 includes a valve main body 2 having a valve chamber VS, a valve element 3, a biasing device 4, an operation rod 5, and a power element 8.

The valve main body 2 includes a first flow path 21, a second flow path 22, an intermediate chamber 221, and a return flow path (also referred to as a refrigerant passage) 23 in addition to the valve chamber VS. The first flow path 21 is a supply-side flow path, and a refrigerant is supplied to the valve chamber VS via the supply-side flow path. The second flow path 22 is a discharge-side flow path, and the fluid in the valve chamber VS is discharged to the outside of the expansion valve through a valve through-hole 27, the intermediate chamber 221 and the discharge-side flow path.

The first flow path 21 and the valve chamber VS are connected with each other by a connecting path 21 a having a smaller diameter than the first flow path 21. The valve chamber VS and the intermediate chamber 221 are connected with each other via the valve seat 20 and the valve through-hole 27.

The operation rod insertion hole 28 formed above the intermediate chamber 221 has a function for guiding the operation rod 5, and the annular recess 29 formed above the operation rod insertion hole 28 has a function of accommodating a ring spring 6. The ring spring 6 has a plurality of spring pieces to apply a predetermined biasing force on the outer circumference of the operation rod 5 by coming into contact therewith.

The valve element 3 is arranged in the valve chamber VS. When the valve element 3 is seated on the valve seat 20 of the valve main body 2, the flow of the refrigerant through the valve through-hole 27 is restricted. This state is referred to as a non-communicating state. However, even in the case that the valve element 3 is seated on the valve seat 20, a limited amount of refrigerant may flow. On the other hand, when the valve element 3 is separated from the valve seat 20, the flow of the refrigerant passing through the valve through-hole 27 increases. This state is referred to as a communication state.

The operation rod 5 is inserted into the valve through-hole 27 with a predetermined gap. The lower end of the operation rod 5 is in contact with the upper surface of the valve element 3. The upper end of the operation rod 5 is fitted into a fitting hole 84 c of the stopper member 84, which will be described later.

The operation rod 5 can press the valve element 3 in a valve opening direction against the biasing force of the biasing device 4. When the operation rod 5 moves downward, the valve element 3 is separated from the valve seat 20 and the expansion valve 1 is opened.

In FIG. 1 , the biasing device 4 includes a coil spring 41 formed by helically winding a wire member having a circular cross section, a valve element support 42, and a spring receiving member 43.

The valve element support 42 is attached to the upper end of the coil spring 41, a spherical valve element 3 is welded to the upper surface thereof, and both are integrated together.

The spring receiving member 43 that supports the lower end of the coil spring 41 can be screwed against the valve main body 2, and has a function of sealing the valve chamber VS and a function of adjusting the biasing force of the coil spring 41.

(Power Element)

Next, the power element 8 will be described. FIG. 2 is an enlarged cross-sectional view of the power element 8, but the differences from the comparative example illustrated by the dotted lines are exaggerated for ease of understanding, and may differ from the actual dimensions. O is set as the axis of the power element 8. The power element 8 includes a plug 81, an upper lid member 82, a diaphragm 83, a receiving member 86, and a stopper member 84. Again, it is assumed that the upper lid member 82 side is the upper side and the receiving member 86 side is the lower side.

The upper lid member 82 is formed, for example, by molding a metal plate material by pressing. The upper lid member 82 includes an annular outer plate portion 82 b, an outer tapered portion 82 c that extends toward the upper side at a shallow angle and is continuously provided on the inner circumference of the outer plate portion 82 b, an inner tapered portion 82 e that extends toward the upper side at a deep angle and is continuously provided on the inner circumference of the outer tapered portion 82 c, and a top portion 82 f which is continuously provided on the inner circumference of the inner tapered portion 82 e. An opening portion 82 a is formed in the center of the top portion 82 f and can be sealed by the plug 81.

The receiving member 86 that opposes the upper lid member 82 is formed, for example, by molding a metal plate material by pressing. The receiving member 86 includes a flange portion 86 a having an outer diameter substantially the same as the outer diameter of the outer plate portion 82 b of the upper lid member 82, a conical portion 86 b that extends the lower side and is continuously provided on the inner circumference of the flange portion 86 a, an annular inner plate portion 86 c continuously provided on the inner circumference of the conical portion 86 b, and a hollow cylindrical portion 86 d continuously provided on the inner circumference of the inner plate portion 86 c. A male screw 86 e is formed on the outer circumference of the hollow cylindrical portion 86 d.

As illustrated in FIG. 1 , a female screw 2 c that engages with the male screw 86 e is formed on the inner circumference of a recess portion 2 a of the valve main body 2 to which the hollow cylindrical portion 86 d is attached.

In FIG. 2 , the diaphragm 83 arranged between the upper lid member 82 and the receiving member 86 is made of a thin and flexible metal (for example, SUS) plate material, and has an outer diameter that is substantially the same as the outer diameters of the upper lid member 82 and the receiving member 86.

More specifically, the diaphragm 83 has an outer circumferential portion 83 a interposed between the upper lid member 82 and the receiving member 86, and a central portion 83 b that comes into contact with the stopper member 84. In addition, the diaphragm 83 is coaxial with the axis O between the outer circumferential portion 83 a and the central portion 83 b, and is provided with a plurality of upper ring-shaped portions 83 c protruding upward and a plurality of lower ring-shaped portions 83 d protruding downward alternately along the radial direction. In the present embodiment, in the cross section illustrated in FIG. 2 , the upper ring-shaped portion 83 c and the lower ring-shaped portion 83 d have a periodic shape such that a substantially sinusoidal curve is formed, but the circumferential groove-shaped upper ring-shaped portion and the lower ring-shaped portion having semicircular cross sections may be independently formed on the flat plate.

FIG. 3 is an enlarged cross-sectional view illustrating a portion A of FIG. 2 according to the present embodiment, and illustrates the displacement position of the diaphragm 83 at the time of maximum valve opening (where the solid line is the neutral position). The outer circumferential portion 83 a is interposed between the outer plate portion 82 b of the upper lid member 82 and the flange portion 86 a of the receiving member 86 to hold the diaphragm 83. The outer circumferential ends of the outer plate portion 82 b, the outer circumferential portion 83 a, and the flange portion 86 a are welded and joined, as will be described later.

The lower ring-shaped portion 83 d closest to the outer circumference of the diaphragm 83 is arranged closer to the outer circumference than the upper ring-shaped portion 83 c closest to the outer circumference of the diaphragm 83, and a gap is formed between the lower ring-shaped portion 83 d and the receiving member 86.

In FIG. 2 , the stopper member 84 has a cylindrical main body 84 a, a disk portion 84 b that is continuously provided on the upper end of the main body 84 a and extends in the radial direction, and a blind hole-shaped fitting hole 84 c formed in the center of the lower surface of the main body 84 a. The disk portion 84 b is in contact with the lower surface of the central portion 83 b of the diaphragm 83.

Next, the assembly procedure of the power element 8 will be described. While placing the stopper member 84 between the diaphragm 83 and the receiving member 86, the outer plate portion 82 b of the upper lid member 82, the outer circumferential portion 83 a of the diaphragm 83, and the flange portion 86 a of the receiving member 86 are overlapped in this order and pressed in the axial direction. Meanwhile, the outer circumference is welded by, for example, TIG welding, laser welding, plasma welding, or the like to form a welded portion W over the entire circumference, such that the components are integrated.

Subsequently, the working gas is sealed in the space (referred to as the pressure working chamber PO) surrounded by the upper lid member 82 and the diaphragm 83 from the opening 82 a formed in the upper lid member 82, and then the opening 82 a is sealed with the plug 81. Further, the plug 81 is fixed to the upper lid member 82 by projection welding or the like.

At this time, since the diaphragm 83 receives pressure in a form of projecting toward the receiving member 86 due to the working gas sealed in the pressure working chamber PO, the central portion 83 b of the diaphragm 83 comes into contact with the upper surface of the stopper member 84 arranged in the lower space (refrigerant inflow chamber) LS surrounded by the diaphragm 83 and the receiving member 86. As a result, the disk portion 84 b of the stopper member 84 is held between the diaphragm 83 and the inner plate portion 86 c of the receiving member 86.

In the present embodiment, when the diaphragm 83 is displaced toward the receiving member 86 and is restrained by coming into contact with the stopper member 84, the diaphragm 83 is in the neutral position (or a position displaced from the neutral position toward the upper lid member side). The “neutral position” refers to a position in which the diaphragm is not subject to a reaction force from a support point on the upper lid member side or from a support point on the receiving member side.

When the diaphragm bends and becomes displaced, the “support point on the upper lid member side” refers to the point on the upper lid member that is in contact with the boundary point between a portion (that does not displace toward the upper lid member side) where the diaphragm is restricted by coming into contact with the upper lid member and a portion displaced toward the upper lid member side. In addition, when the diaphragm bends and becomes displaced, the “support point on the receiving member side” refers to the point on the receiving member that is in contact with the boundary point between a portion (that does not displace toward the receiving member side) where the diaphragm is restricted by coming into contact with the receiving member and a portion displaced toward the receiving member side.

Here, it is preferable that the support point on the receiving member 86 side is closer to the outer circumference of the diaphragm 83 than the support point on the upper lid member 82 side.

When the power element 8 assembled as described above is attached to the valve main body 2, the axis O is aligned with the axis L, and the male screw 86 e on the outer circumference of the lower end of the hollow cylindrical portion 86 d of the receiving member 86 engages with the female screw 2 c formed on the inner circumference of the recess portion 2 a of the valve main body 2. When the male screw 86 e of the hollow cylindrical portion 86 d is screwed with respect to the female screw 2 c, the inner plate portion 86 c of the receiving member 86 comes into contact with the upper end surface of the valve main body 2. As a result, the power element 8 can be fixed to the valve main body 2.

At this time, a packing PK is interposed between the power element 8 and the valve main body 2, and the space in the recess portion 2 a connected to the lower space LS is sealed to prevent the refrigerant from leaking from the recess portion 2 a. In this state, the lower space LS of the power element 8 communicates with the return flow path 23 via the communication hole 2 b.

(Operation of the Expansion Valve)

An example of the operation of the expansion valve 1 will be described with reference to FIG. 1 . The refrigerant pressurized by the compressor 101 is liquefied by the condenser 102 and sent to the expansion valve 1. Further, the refrigerant adiabatically expanded by the expansion valve 1 is sent to the evaporator 104, and the evaporator 104 exchanges heat with the air flowing around the evaporator. The refrigerant returning from the evaporator 104 is returned to the compressor 101 side through the expansion valve 1 (more specifically, the return flow path 23). At this time, by passing through the evaporator 104, the fluid pressure in the second flow path 22 becomes larger than the fluid pressure in the return flow path 23.

A high-pressure refrigerant is supplied to the expansion valve 1 from the condenser 102. More specifically, the high-pressure refrigerant from the condenser 102 is supplied to the valve chamber VS via the first flow path 21.

When the valve element 3 is seated on the valve seat 20 (when in the non-communicating state), the flow rate of the refrigerant sent from the valve chamber VS to the evaporator 104 through the valve through-hole 27, the intermediate chamber 221 and the second flow path 22 is limited. On the other hand, when the valve element 3 is separated from the valve seat 20 (when in the communicating state), the flow rate of the refrigerant sent from the valve chamber VS to the evaporator 104 through the valve through-hole 27, the intermediate chamber 221 and the second flow path 22 increases. Switching between the closed state and the open state of the expansion valve 1 is performed by the operation rod 5 connected to the power element 8 via the stopper member 84.

In FIG. 1 , a pressure working chamber PO and a lower space LS partitioned by a diaphragm 83 are provided inside the power element 8. Accordingly, when the working gas in the pressure working chamber PO is liquefied, the diaphragm 83 and the stopper member 84 rise, such that the operation rod 5 moves upward according to the biasing force of the coil spring 41. On the other hand, when the liquefied working gas is vaporized, the diaphragm 83 and the stopper member 84 are pressed downward, such that the operation rod 5 moves downward. In this way, the expansion valve 1 is switched between an open state and a closed state.

Further, the lower space LS of the power element 8 communicates with the return flow path 23. Accordingly, the volume of the working gas in the pressure working chamber PO changes according to the temperature and pressure of the refrigerant flowing through the return flow path 23, and the operation rod 5 is driven. In other words, in the expansion valve 1 illustrated in FIG. 1 , the amount of the refrigerant supplied from the expansion valve 1 toward the evaporator 104 is automatically adjusted according to the temperature and pressure of the refrigerant returning from the evaporator 104 to the expansion valve 1.

Comparative Example

Next, the effects of the present embodiment will be described with reference to a comparative example. In FIG. 2 , for ease of understanding, a stopper member 84A according to the comparative embodiment (illustrated by the dotted line) is shown superimposed on the stopper member 84 of the present embodiment. The stopper member 84A according to the comparative example differs from the stopper member 84 of the present embodiment only in the thickness of the disk portion. More specifically, the thickness t_(A) of the disk portion 84Ab of the stopper member 84A is smaller than the thickness t of the disk portion 84 b of the stopper member 84 (t_(A)<t). The shape of the power element 8′ of the comparative example other than the stopper member 84A is the same as that of the power element 8 of the present embodiment.

In the power element 8′ of the comparative example, when the working gas in the pressure working chamber PO expands, the diaphragm 83 is displaced toward the receiving member 86, and the diaphragm 83 comes into contact with the stopper member 84 and is restrained (that is, when the valve is completely open), a disk portion 84Ab is interposed between the diaphragm 83 and the inner plate portion 86 c of the receiving member 86, as illustrated by the dotted line in FIG. 2 . At this time, since the thickness t_(A) of the disk portion 84Ab is relatively thin, the diaphragm 83 is in a position displaced from the neutral position toward the receiving member 86 side. Accordingly, as illustrated by the dotted line in FIG. 3 , the diaphragm 83 is displaced toward the receiving member 86 side, so that the reaction force is received from the support point P1 on the receiving member 86 side. In other words, the diaphragm 83 is displaced from the neutral position around the support point P1 on the receiving member 86 side, whereby the gap between the diaphragm 83 and the receiving member 86 increases or decreases.

Here, during the operation of the refrigeration circulation system 100, foreign matter DS such as metal powder mixed in the refrigerant may enter the lower space LS via the return flow path 23. In such a case, as illustrated in FIG. 3 , the foreign matter DS may enter the gap between the diaphragm 83 and the receiving member 86, and the foreign matter DS may be caught between the diaphragm 83A and the receiving member 86 when the diaphragm 83 is displaced toward the receiving member 86. Since the diaphragm 83 is formed of a very thin metal plate, when the relatively hard foreign matter DS becomes caught, stress concentration may occur, causing local deformation and, in some cases, deteriorating the operating characteristics of the power element 8.

In contrast, according to the present embodiment, when the diaphragm 83 is displaced toward the receiving member 86 and is restricted by coming into contact with the disk portion 84 b of the stopper member 84, the diaphragm 83 is in the neutral position (or a position displaced from the neutral position toward the upper lid member side) illustrated by the solid line in FIG. 3 . That is, the diaphragm 83 is displaced with respect to the support point P2 on the upper lid member 82 side only within a range from the neutral position to the upper lid member 82 side between the time of maximum valve opening and the time of valve closing. In other words, since the diaphragm 83 does not displace from the neutral position toward the receiving member 86 side, even if foreign matter DS enters the gap between the diaphragm 83 and the receiving member 86, since the gap does not become small, the foreign matter does not get caught and local deformation of the diaphragm 83 or the like does not occur. As a result, a normal strainer (not illustrated in the figures) used in the refrigerant circulation system 100 can be used, and the efficiency of transporting the refrigerant is not reduced.

Second Embodiment

FIG. 4 is a schematic cross-sectional view illustrating the expansion valve 1A according to the second embodiment. FIG. 5 is a cross-sectional view of the power element 8A according to the second embodiment. FIG. 6 is a cross-sectional view illustrating an enlarged portion B of FIG. 4 according to the second embodiment.

The expansion valve 1A illustrated in FIG. 4 differs from the expansion valve 1 according to the first embodiment in the upper configuration of the power element 8A and the valve main body 2A. That is, in the present embodiment, the power element 8A and the valve main body 2A are not connected by engaging a screw, and the connection between the two is performed by caulking. Since the rest of the configuration is the same as that of the first embodiment, the same reference numerals are given and redundant description will be omitted.

In FIG. 5 , the power element 8A includes a plug 81, an upper lid member 82, a diaphragm 83, a receiving member 86A, and a stopper member 84. Again, it is assumed that the upper lid member 82 side is the upper side and the receiving member 86A side is the lower side. It should be noted that the stopper member need not be provided, but in this case, it is preferable to provide a restraining member for restraining the displacement of the diaphragm in place of the stopper member. A portion of the receiving member 86A may be deformed to replace the stopper member.

In the power element 8A according to the present embodiment, only the configuration of the receiving member 86A is primarily different from that of the power element 8 according to the first embodiment. Since the plug 81, the upper lid member 82, the diaphragm 83, and the stopper member 84 have basically the same configuration except for minor differences in shape, the same reference numerals are given and redundant description will be omitted.

The receiving member 86A formed by molding a metal plate material by pressing includes a flange portion 86Aa having an outer diameter substantially the same as the outer diameter of the outer plate portion 82 b of the upper lid member 82, a conical portion 86Ab that extends the lower side and that is continuously provided on the inner circumference of the flange portion 86Aa, an annular intermediate plate portion 86Ae continuously provided on the inner circumference of the conical portion 86Ab, a hollow cylindrical portion 86Ad continuously provided on the inner circumference of the intermediate plate portion 86 c, and an annular inner plate portion 86Ae continuously provided on the inner circumference of the hollow cylindrical portion 86Ad. The inner plate portion 86Ae includes a central opening portion 86Af into which the main body 84 a of the stopper member 84 is fitted.

When assembling the power element 8A, while placing the stopper member 84 between the diaphragm 83 and the receiving member 86A, the outer plate portion 82 b of the upper lid member 82, the outer circumferential portion 83 a of the diaphragm 83, and the flange portion 86Aa of the receiving member 86A are overlapped in this order and pressed in the axial direction. Meanwhile, the outer circumference is welded by, for example, TIG welding, laser welding, plasma welding, or the like to form a welded portion W over the entire circumference, such that the components are integrated.

Subsequently, the working gas is sealed in the space surrounded by the upper lid member 82 and the diaphragm 83 from the opening 82 a formed in the upper lid member 82, and then the opening 82 a is sealed with the plug 81. Further, the plug 81 is fixed to the upper lid member 82 by projection welding or the like. In this way, the power element 8A can be assembled.

In FIG. 6 , the valve main body 2A formed of a metal such as aluminum includes a circular tube portion 2 d extending from the upper end thereof. The inner diameter of the circular tube portion 2 d is equal to or slightly larger than the outer diameter of the power element 8A.

Prior to attaching the power element 8A to the valve main body 2A, the circular tube portion 2 d has a cylindrical shape coaxial with axis L (FIG. 4 ), as illustrated by the dotted line. When attaching the power element 8A to the valve main body 2A, an annular packing PK is arranged on the step portion 2 e of the valve main body 2A, and the power element 8A is made to approach the valve main body 2A from the receiving member 86A side, and is fit into the circular tube portion 2 d. At this time, the packing PK is interposed between the intermediate plate portion 86Ac and the step portion 2 e.

In this state, when the tip of the circular tube portion 2 d is caulked inward using a caulking tool (not illustrated in the Figures), the tip of the circular tube portion 2 d is plastically deformed toward the axis L to form an annular caulked portion 2 f. The outer circumferential upper surface of the outer plate portion 82 b of the upper lid member 82 is pressed and fixed by the caulked portion 2 f. As a result, the packing PK is compressed in the axis L direction between the intermediate plate portion 86Ac and the step portion 2 e, the space in the recess portion 2 a connected to the lower space LS is sealed, and leakage of the refrigerant from the recess portion 2 a is prevented.

The expansion valve 1A illustrated in FIG. 4 can also be incorporated into the refrigerant circulation system 100 illustrated in FIG. 1 , and exhibits the same functions as the expansion valve 1 according to the first embodiment.

It should be noted that the present invention is not limited to the above-described embodiments. Within the scope of the present invention, any component of the above-described embodiments can be modified. In addition, any component can be added or omitted in the above-described embodiments. For example, in the present embodiment, the position of the diaphragm at the time of maximum valve opening is set to the neutral position, but the position displaced from the neutral position toward the upper lid member side may be set as the position at the time of maximum valve opening.

REFERENCE SIGNS LIST

-   1, 1A . . . Expansion valve -   2, 2A . . . Valve main body -   3 . . . Valve element -   4 . . . Biasing device -   5 . . . Operation rod -   6 . . . Ring spring -   8, 8A . . . Power element -   20 . . . Valve seat -   21 . . . First flow path -   22 . . . Second flow path -   221 . . . Intermediate chamber -   23 . . . Return flow path -   27 . . . Valve through hole -   28 . . . Operation rod insertion hole -   29 . . . Annular recess -   41 . . . Coil spring -   42 . . . Valve element support -   43 . . . Spring receiving member -   81 . . . Plug -   82 . . . Upper lid member -   83 . . . Diaphragm -   84 . . . Stopper member -   86, 86A . . . Receiving member -   100 . . . Refrigerant circulation system -   101 . . . Compressor -   102 . . . Condenser -   104 . . . Evaporator -   VS . . . Valve chamber 

1. A power element comprising: a diaphragm; an upper lid member that comes into contact with an outer circumferential portion of the diaphragm and that forms a pressure working chamber with the diaphragm; a receiving member that comes into contact with an outer circumferential portion of the diaphragm and that forms a refrigerant inflow chamber with the diaphragm; and a stopper member housed in the refrigerant inflow chamber and in contact with the diaphragm, wherein the diaphragm is displaced within a range from a neutral position to a position displaced from the neutral position toward the upper lid member side.
 2. The power element according to claim 1, wherein the diaphragm is restrained by the receiving member via the stopper member within a range from the neutral position to a position displaced from the neutral position toward the upper lid member side.
 3. The power element according to claim 1, wherein a support point on a receiving member side is closer to an outer circumference of the diaphragm than a support point on an upper lid member side.
 4. An expansion valve comprising: a power element; a valve main body provided with a refrigerant flow path communicating with a refrigerant inflow chamber, having a valve chamber and a valve seat; a valve element disposed in the valve chamber; a coil spring that presses the valve element toward the valve seat; and an operation rod having one end in contact with the valve element, wherein: the power element includes a diaphragm, an upper lid member that comes into contact with an outer circumferential portion of the diaphragm and that forms a pressure working chamber with the diaphragm, and a receiving member that comes into contact with an outer circumferential portion of the diaphragm and that forms the refrigerant inflow chamber with the diaphragm, and the diaphragm is displaced within a range from a neutral position to a position displaced from the neutral position toward the upper lid member side by a pressure difference between a pressure working chamber of the power element and the refrigerant inflow chamber, and drives the valve element against a biasing force of the coil spring.
 5. The expansion valve according to claim 4, wherein: the power element includes a stopper member housed in the refrigerant inflow chamber and in contact with the diaphragm; and the diaphragm is restrained by the receiving member via the stopper member within a range from the neutral position to a position displaced from the neutral position toward the upper lid member side. 